Maria Faustina Kowalska was born on August 25, 1905, in Głogowiec, Poland. From a young age, she felt a deep calling to religious life and, after overcoming family resistance, joined the Congregation of the Sisters of Our Lady of Mercy in 1925. As a nun, she experienced profound mystical visions, during which Jesus revealed to her the message of Divine Mercy, emphasizing God's boundless compassion for humanity. At His instruction, she kept a diary detailing these encounters, which later became the foundation for the Divine Mercy devotion. Sister Faustina passed away on October 5, 1938, in Kraków, Poland, after suffering from tuberculosis.

The cause for her beatification began in 1965, initiated by Karol Wojtyła, then Archbishop of Kraków and later Pope John Paul II. She was beatified on April 18, 1993, and canonized on April 30, 2000, by Pope John Paul II, who declared the Second Sunday of Easter as Divine Mercy Sunday for the universal Church. Her feast day is celebrated on October 5.

During her canonization, Pope John Paul II remarked, "Jesus said to Sr. Faustina one day: 'Humanity will never find peace until it turns with trust to Divine Mercy.'"